Spark plug



Nov. 1, 1938. G PAULS'QN 2,135,240

SPARK PLUG Filed Sept. 12,, 1932.

' Fig.1.

1 v I INVENTOR- Patented Nov. 1, 1938 UNITED STATES SPARK PLUG.

George M. Paulson, New York, N. 1., assignor to The B. G. Corporation,New York, N. Y., a corporationof New York Application September 12,1932, Serial No. 632,745 10 Claims. (01. 123-169) This invention relatesto spark-plugs, and more especially to spark-plugs for use in aviationengines.

The object of the invention has been to provide a spark-plug which wouldgive. superior, re-

liable and long service under the .conditions to. which aviationspark-plugs are subjected, and even when very high compressions, withextreme super-charging, are restarted to.

A further object has been to provide an"aviation spark-plug which, undermost difficult conditions, would not heat up to the point of causingpre-ignition.

A further object has been to provide a. construotion which would protectthe core and keep it relatively cool under such conditions.

A particular object of the invention is to provide an improved electrodeconstruction or combination which gives the maximum length of servicewithout adjusting or re-setting the gap. A further object is to providea construction with which it is easyto adjust the gap when it doeseventually burn away sufliciently to require resetting, and which can bere-set repeatedly, for

successive long periods of service.

Another particular object is to provide the maximum amount of metal toburn away at the gap and-a maximum amount of heat conduction to the bodyor shell of the plug.

Another object is to provide a spark-plug having the maximum amount ofarea ofmetal at the.

gap and which can stfll be easily adjusted.

Another object is to provide the maximum amount of metal at the gap witha comparatively small amount of metal exposed to. the high cylindertemperatures. v j

A-furtherobject is to provide a construction with which there is nodanger of longitudinal expansion of the-electrode elements closing the40 gap suiiiciently to produce a short circuit.

- Still another object'is to provide a construction which promotes theflow of gases intoand. out of the plug.

Another object is to provide a construction which is easy and economicalto manufacture.

The invention relates to the type of sparkplug having several electrodeprongs-extending from the body or shell into proximity "to a centralelectrode, and more especially to the kind of construction in whichthese prongs are cut or formed from a disc or baflle of a metal or alloywhich is resistant to the spark in the presence of cylinder gases, thisbaiiie being united to the shell, which is usually of a different metal.The

is prongs or pronged baiiie provide a plurality Of spark gaps, and'bypartly closing the chamber of the shell, into which the core projects,and by carrying heat off into the shell protect the core from toointense radiant heat and shield it more or less from lubricating oil.The shell electrode- 5 should not substantially close the inner end ofthe core chamber, since a comparatively large orifice area aids inpreventing overheating. The construction disclosed herein provides ampleorifice area. By properly proportioning the solid 10 area of the baffleongroup' of prongs, the spaces between the prongs and the amount anddistribution ofmetal in the baflle, and if there be enough heatconduction from the bailie into the shell, it is possible to shield thecoresufilciently from 15 temperatures on the order of 2600"F. or higher,and still enable the multiple gap electrode to function satisfactorilyand not superheat itself or the plug to a point of failure. Theelectrode. baflle, or the group of prongs, must be heavy in order tostand up and save itself and the'core from excessive heating, but not soheavy as to be an accumulator of heat.

In a prior application, now Patent No. 1,959,639,1ssued May 22, 1934, Ihave set forth the discovery of the cause of'failure of electrode bafliespark-plugs of ordinary construction when I subjected to severeconditions in aviation engines, and a solution of the "difliculty, whichwas to unite the baille to the shell by a thorough, fused joint. Theprior practice was to clamp the edge of, the baflie in a groove of theshell by crimping the end of the shell under the baiiie, a plan whichapparently produced a perfectlysolid construction, but which, I becameconvinced, di permit gases to enterthe joint and cause dete oration,reducing the capacity of the shell to draw oil. heat from the baflleuntil, after more or less service, the baflle would overheatsufliciently to cause pre-ignition, this in turn causing the .sparking40 points to burn away quickly.

The'constructionclaimed in my former appli v cation is embodied in thespark plug disclosed herein, and is highly important incombination withthepresent improvements.

The other features of this invention relate'to the form and relation ofa central electrode head and the opposed or surrounding electrodeprongs. Briefly, the head of'the spindle or central electrode is ratherlike an inverted truncated cone, with its sides preferably incurved atthe sparkg'ap in axial planes,'while the stout prongs; in stead ofextending radially inward, or in a cupwise manner, from the baflie orshell, are directed inward and steeply downward and preferably on aconvex curvature, substantially paralleling the lines of the head. Theresult is to produce a much deepened or vertically extended multiplesparkgap, with so much metal and surface at the gap both to the presenceof a large amount of 'metal to burn away very slowly and to a maximumamount of heat conductivity.

Other advantages of the invention have already" been indicated, and tothese should be added the .fact that the construction makes possible aspindle head of minimum length.

In the accompanying drawing, illustrating a plug the sparking surfacesof the prongs are conpreferred embodiment of the invention:

Fig. 1 is aview-of the spark-plug with the lower part in section and therest of the plug in elevation; and i Fig. 2 is a bottom plan viewlookingjat the innor end of. the plug.

The body or shell of the spark-plug is designated by the referencecharacter 2, and 3 'is the central spindle. The spark-plug ispreferably-and typically of themica-insulated class. .A knownconstruction is shown in which the spindle is surrounded first by asleeve 4 of rolled mica, this sleeve being compressed against thespindle by means, including a nut 5, to produce a leak-tight dam, and inwhich a stack 6 of mica washers in the chamber 1 of the plug is heldunder compression between the head 8 of thespindle andan abutment in theshell, and another stack 9 of mica discsis held under compressionbetween the nut and the top piece In over which the upper end of thespindle is upset.

-' Heretofore the electrode or sparking end of the spindle of aspark-plug has usually been a com paratively narrow cylinder, and in aconstruction such as illustratedthe head or lower portionof the spindlehas been rounded inward below the shoulder, with the cylindricalelectrode projection extending downward from the convexity.

The spindle head 8 of the spark-plug shown in the drawing is relativelyshort as compared with truncated lower end ll.

a head and pin-like sparking projection such as shown in my Patent No.1,959,639, for example,

and it tapers downward from a broad base to a The precise form may bevarled,bu't the best results are secured by concaving the lines I! ofthe sides'of the head coextensively with the deep spark-gap l3. For theshort distance above the gap, the curvature M of the head is preferablyconvex, this reverse curvature being advantageous.

The electrode baiile l5 may be understood to be of a nickelmanganesealloy or some other shell, and at the present time being more conmetalor alloy resistant to the spark, and which It. is

can be bent repeatedly without injury. placed in an open bottom seat inthe lower end of the shell or body 2 and is secured in place by a fusedbend it as in my patent aforesaid. This.

. bond may be made by welding. or brazing, the "latter bond, whichinvolves a third metal, being adequateto resist the heat and insuringperfect heat conductivity as between the baiiie'and the venient forproduction purposes than welding.

f This disc and its set ofv sparking prongs 26 are of considerablethickness, a thickness on the order I of .080" being sufllcient (thisbeing given by way of example). The prong'sare of substantial width andare preferably three or more in number (four being very satisfactory),symmetrically disposed about the center. The openings I1 between theprongs are relatively large. In the end view of the plug the prongsappear to be substantially radial, but seen in vertical section theyturn downward quite precipitously, bringing their blunt end faces evenwith the end face ll of the.

head and their sloping inner side surfaces l9 into opposition to thesides J! of the head across the 'spark-gaplil. The prong surfaces I 9are preferably conve'xly curved in axial planes on a curvaturesubstantially corresponding to that of the lines l2 of the head, so thatthe spacing is virtually uniform throughout a gap of very considerabledepth.

In planes at right angles to the axis of the the shell, and obviouslythe improvements may be applied to the mechanically locked or crimplocktype of baiiie construction, with advantages as compared with priorpractice but with considerable sacrifice of benefits as compared withthe preferred embodiment of this invention.

v While a spark-plug constructed in accordance with my invention hasbeen described in detail it will be understood that various changes maybe made without departing from essentials.

I claim: 1. A spark-plug having a shell, a downwardly tapering centralelectrode, and a set of massive prongs united with the lower end of theshell and constituting ground electrodes, said ground elec- I trodesextending inward from the shell and being directed steeply downwardaround the central of the central electrode, so that there is a deep andlarge spark gap surface area between the central and ground electrodes,with a large se'ction in the ground electrodes to carry off heat intothe shell, the ground electrodes being adjustable by-deflecting theirdownturned portionsinwardly, so that in such adjustment the large sparkgap surface area may be maintalned .saidground electrodes being formedin a bailie which is cutout between the prongs, the periphery of saidbaflie being united to theshell by a fused, heat-conducting bond.

2. A spark-plug having a shell, a'downwardly and concavely taperedcentral electrode, and a set of stoutprongs united with the lower end ofthe shell and constituting ground electrodes, said ground electrodesextending inward from the shell and being directed steeply downward in aconvex curvature and having broad inner surfaces which substantiallyfollow the curvature of the central electrode, the formation of saidground electrodes and their relation to the central electrodes beingsuch that there is a large spark gap surface area between the centralelec-- trode and the ground electrodes. a

3. A spark plug having a shell, a downwardly and'concavely taperedcentral electrode, and a set of stout prongsunited with the lower end ofthe shell and constituting ground electrodes, said I and extendinginward having inner side surfaces cross-axially curved concentricallywith and extending downwardly spindle head to circumferen-' tially and,longitudinally conform thereto and ground electrodes extendinginwardffrom the shell and being directed steeply downwardin a convexcurvature which substantially follows the curvature of the centralelectrode, the formation of said ground electrodes and their relation tothe central electrodes being such that there is a large spark gapsurface area between the cen-, tral electrode andthegroundelectrodes,the inner side surfaces of said prongs being convexly curved in axialplanes and concavely curved-in transverse planes.

1 4. A spark plug having a shell, a central electrode with asubstantially cone shaped head and a set of massive prongs united withthe lower end of the'shell and constituting ground electrodes, innerside surfaces of to the shape of the center electrode head, so thatthere is a deep and large spark gap surface area between the center andground electrodes, which said gap may easily and by a narrow strip orwire gauge feelers, with a large section in the ground of! heat into theshell, the ground electrodes being adjustable by deflecting their downturned portions inward, so that in such adjustment the large spark gapsurface area may be maintained' 5. A spark plug having a shell,-adownwardly and substantially uniformly tapering center electrode headand a set of prongs united with the lower end of the shell constitutingthe ground electrodes, 'saidgrou'nd electrodes being flattened from theshell and being shaped concentrically around and directed down thetapered center electrode head so as to furnish large surface areas forthe spark gap and a large section in the electrodes for conducting heatto the shell, as well as to be flexible enough for adjustment of thegap. I

6. A spark plug having a shell, a downwardly tapering circular spi dlehead, and a set of stout ground electrodes su ported by the shell andextending inwardly and downwardly therefrom and along the circularcollectively surround the greater part of the circumference ofthecomplementai y-portion of the spindle'head at the gap, so as tofurnish a plu rality, of large surface areas for the spark gap,-

with a large section in each ground electrode for conducting heat' tothe shell, said ground electrodes being adjustable by bending themradially of the plug, so that, by such adjustment, thelarge surfaceareas for the spark gap may be maintained.

. 7. A spark plug having a shell, a-downwar'dly tapering circularspindle head, and a set of stout,

ground electrodes supported by the shell and extending inwardly anddownwardly therefrom and having inner side surfaces cross-axially curvedconcentrically with and extending downwardly.

along the circular spindle head to circumferentially and longitudinallyconform thereto, with the said prongs conforming 1 accurately bemeasured electrodes to carry spark gap, with a large section in eachground constituting ground I electrodes, said gr able by deflectingtheir downturned portions in- "is out at least the lower end portions ofsaid surfaces collectively surrounding the greater part of thecircumference of thejuxtaposed portion of the spindle head,-so as tofurnish a plurality of large surface areas for the spark gap, with alarge section in each ground electrode for conducting heat to the shell,said ground electrodes being adjustable by bending them radially of the.plug so that, by such adjustment, the large surface areas for the sparkgap may be maintained.

8. Aspark plug having a shell, a downwardly tapering circular spindlehead, and a set of stout ground electrodes supported by the shell andex- I tending portions thereof, inner side surfaces cross-axially curvedconcentrically with and ex-' tending downwardly along the circularspindle head to circumferentiallyand longitudinally conform thereto,with at least the lower end portions of said surfaces collectivelysurrounding the greater part of the circumference of 'the juxtaposedportion of the spindle head, so as to furnish a plurality of largesurface areas forthe electrode for conducting heat to the shell, saidground electrodes their downwardly extending portions radially of theplug so that, by such adjustment, the large surface areas forthe sparkgap may be main'. tained. I

9. A spark-plug having a shell, a downwardly tapering central electrode,and a set of massive prongs unitedwiththe, lower end of the shell and mmelectrodes extending inward from the shell, and being directed steeplydownward around the central electrode and so formed that their innerside surfaces substantially follow the lines ofthe sides of the central,electrode, so that there is a deep and large spark gap surface areabetween the central and ground electrodes, with a large section in theground electrodes to carry off heat into the shell, the groundelectrodes being adjustwardly, so that in such adjustment the largespark gap surfacev area may be'maintained, said ground electrodes beingformed in-a baflle which out between the prongs, the said baille beingsupported at its-periphery adjacent the, lower end of the shell andmaking good heat-conducting and electrical connection therewith.

10. A spark-plug having a shell, a downwardly tapering central electrodehead, and a set of prongs united with the lower end of the shell furnishlarge surface areas being adjustable" by bending constituting groundelectrodes, said ground elec- I I the ground electrodes being likewiseof large section for conduction of heat to the shell, yet flexibleenough for adjustment of the gap.

GEORGE M. PAUL-SON.

